1. Technical Field
This application discloses an opto-electronic device and more particularly to the light-emitting device having a multi-quantum well structure.
2. Reference to Related Application
This application claims the right of priority based on TW application Ser. No. 097132545, filed Aug. 25, 2008, entitled “OPTO-ELECTRONIC DEVICE”, and the contents of which are incorporated herein by reference.
3. Description of the Related Art
The light-emitting diodes (LEDs) have the characteristics of small volume, long operational life, low driving voltage, low power consumption, quick response, and shockproof so the LEDs have been widely used in cars, computers, communications, and consumer electronics products.
Generally speaking, the light emitting diodes (LEDs) have an active layer sandwiched by two cladding layers having different conductivity type (for example, the p-type and the n-type cladding layers). When applying a driving voltage to the contact electrodes located on the two cladding layers, the electrons and the holes from the two cladding layers will be injected into the active layer, and combine in the active layer to generate light. The light is omnidirectional and is extracted from every surface of the light emitting diodes. Usually, the active layer can be a single quantum well structure or a multi-quantum well structure. Comparing to the single quantum well structure, the multi-quantum well structure has better opto-electronic converting efficiency. It can convert current into light through a small bandgap structure alternately arranged by many quantum barrier layers and many quantum well layers even when the input current is small.
However, the multi-quantum well structure is easily influenced by the carrier overflow effects and the piezoelectric field effect which makes it difficult to limit the electrons and holes in the multi-quantum well structure efficiently for combination so the light extraction efficiency of the light emitting diodes can't be improved efficiently.